EP1330502A2

EP1330502A2 - Coating composition

Info

Publication number: EP1330502A2
Application number: EP01992744A
Authority: EP
Inventors: Wylie Wetzel; George William O'dell
Original assignee: Valspar Sourcing Inc
Current assignee: Sherwin Williams Co
Priority date: 2000-10-31
Filing date: 2001-10-31
Publication date: 2003-07-30
Anticipated expiration: 2021-10-31
Also published as: ATE268367T1; EP1330502B1; AU2002225834A1; US6509417B1; WO2002036692A2; WO2002036692A3; DE60103657D1; DE60103657T2

Abstract

A multi-component coating composition having a hard, glossy, and tack-free finish is described. The coating composition comprises a fatty acid modified glycidyl-containing component and a hydroxy-functional polymer. The coating composition can be used to originally finish or to refinish such articles as farm, industrial, and construction equipment, automobiles, and trucks, and to paint structures such as bridges, buildings, appliances, metal furniture, and the like.

Description

COATING COMPOSITION

The present invention relates to a multi-component coating composition. More particularly, the invention relates to a multi-component coating composition comprising a fatty acid modified glycidyl-contaming component and a hydroxy-functional polymer.

BACKGROUND

There are a wide variety of multi-component coating compositions available for finishing substrates. Typically, the components are mixed together before application, and the resulting composition is applied by conventional techniques, such as spraying, roll coating, curtain coating, dipping, or flow coating. The applied composition is then cured at ambient or at elevated temperatures. Such compositions are typically used to finish or to refmish surfaces on farm, industrial, and construction equipment, automobiles, and trucks, and to provide durable protective coatings on bridges, buildings, appliances, metal furniture, and the like.

Most multicomponent coatings are formulated immediately before use by combining at least two reactive binder components, each typically solved based and each a prepolymer or mixture of prepolymers having functional groups reactive with one or more functional groups on the second reactive binder component.

Exemplary of some of the multicomponent coatings compositions that have been in use are those based on anhydride and glycidyl functional prepolymers, for example, polyepoxides. Each of such compositions exhibits advantages in terms of coating performance, but has as well disadvantages, for example, high viscosity, short shelf- life and required high temperature cure.

While research efforts in recent years have produced significant technical advances in multicomponent coating compositions, there is still a need for a coating composition that cures at ambient temperatures to provide a high quality, durable finish for exterior decorative or protective coating applications for industrial, agricultural, and construction equipment, and the like, that exhibits superior substrate surface adhesion, good weatherability, and that has a pleasing appearance. SUMMARY OF THE INVENTION

Such favorable coating performance characteristics are provided by the multicomponent compositions of the present invention prepared by blending reactive binder components: 1) a fatty acid modified glycidal functional polymer having hydroxy functionality, glycidal functionality and olefin functionality (unsaturated groups), and 2) a polyhydroxy functional polymer having a weight average molecular weight of about 3000 to about 20,000 and preferably including tertiary amine catalyst functionality; and a solvent. The present compositions are characterized in part by their inherent low viscosity. Lowered viscosity results in better sprayability, and reduces the amount of environmentally hazardous volatile organic compounds required as less quantities of organic solvent are necessary to obtain a coating composition with the desired viscosity. The present coating compositions provide hard, glossy and tack-free finishes with ambient temperature cure conditions.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present coating composition comprises about 20 to about 80 percent by weight of a solvent and about 20 to about 80 percent by weight of reactive binder components wherein the binder components comprise:

(a) 0 to about 24 percent based on the binder weight of an anhydride acrylic polymer having at least two reactive anhydride groups and comprising the product of polymerization of monomers of an ethylenically unsaturated anhydride or an ethylenically unsaturated dicarboxylic acid and monomers^' selected from the group consisting of C_rC_g alkyl methacrylate, C_rC₈ alkyl acrylate, vinyl monomers and mixtures thereof, the acrylic polymer having a weight average molecular weight of about 2,000 to about 50,000;

(b) about 5 to about 50 percent based on the binder weight of a fatty acid modified glycidyl component having hydroxy functionality and at least two reactive glycidyl groups and at least two reactive unsaturation groups; and

(c) about 5 to about 60 percent based on the binder weight of a polymeric component containing multiple hydroxy groups selected from the group consisting of acrylic polyols, polyester polyols, polyesterurethane polyols, polyether polyols, acrylourethane polyols and any mixtures thereof and having a weight average molecular weight of about 3,000 to about 20,000. In one embodiment, the hydroxy functional polymeric component further comprises about 0J to about 15 percent, based on the binder weight, of a catalyst (for example, a compound having a tertiary amine functionality) incorporated into the polymer, and up to about 25 percent based on the binder weight of an aromatic vinyl, such as styrene.

In one embodiment of the invention the glycidyl component is selected from the group consisting of a polyglycidyl ether of a low molecular weight polyol, an epoxy resin of epichlorohydrin and bisphenol A, a polyglycidyl ester of polyacids, polyglycidyl ethers of isocyanurates, a glycidyl methacrylate or a glycidyl acrylate containing acrylic polymer, and mixtures thereof. The glycidyl polymeric component is modified with an unsaturated fatty acid, for example, one from the group consisting of a dehydrated caster oil fatty acid, a tall oil fatty acid, a soya oil fatty acid, a linseed oil fatty acid, and a coconut fatty acid.

In those compositions of this invention including, as a reactive binder component, an anhydride acrylic polymer, the anhydride acrylic polymer consists essentially of about 20 to about 40 percent by weight, based on the weight of the acrylic polymer, of methyl methacrylate, styrene, or mixtures thereof, about 35 to about 55 percent by weight of an alkyl methacrylate or an alkyl acrylate having 2-4 carbon atoms in the alkyl group and about 5 to about 55 percent by weight of polymerizable ethylenically unsaturated anhydride or ethylenically unsaturated dicarboxylic acid. Optionally the anhydride acrylic polymer can be formed to contain about 0J to about 50 percent by weight of monomers selected from the group consisting of styrene acrylonitrile, methacrylonitrile and mixtures thereof.

The reactive binder polymeric component containing multiple hydroxy groups is typically a polymer comprising polymerized monomers of a hydroxy alkyl methacrylate or an hydroxy alkyl acrylate and polymerized monomers selected from the group consisting of alkyl methacrylate, alkyl acrylate and mixtures thereof, wherein the alkyl groups have 1-12 carbon atoms and the polymer has a weight average molecular weight of about 3,000 to about 20,000. The polymeric component containing multiple hydroxy groups can contain about 0J to about 50 percent by weight of monomers selected from the group consisting of styrene, acrylonitrile, methacrylonitrile, and mixtures thereof. In one particularly useful embodiment the hydroxy functional reactive binder component is formulated to have catalyst functionality in the polymer, for example, tertiary amine functionality introduced by including tertiary amine functional acrylates or methacrylates in the prepolymer mixture from which the hydroxy functional reactive binder component is prepared. In another embodiment of the invention there is provided a coating composition having a hard, glossy and tack-free finish. The coating composition comprises about 50 to about 90 percent by weight of reactive binder components and about 10 to about 40 percent by weight of an organic solvent wherein the reactive binder components comprise (a) about 1 to about 20 percent by weight, based on the binder weight, of an anhydride acrylic polymer having at least two reactive anhydride groups and comprising the product of polymerization of monomers of an ethylenically unsaturated anhydride and monomers selected from the group consisting of C_rC₈ alkyl methacrylate, C_rC₈ alkyl acrylate, aromatic vinyl monomers and mixtures thereof, wherein the alkyl groups have 1-8 carbon atoms and wherein the acrylic polymer has a weight average molecular weight of about 2,000 to about 40,000; (b) about 20 to about 80 percent by weight, based on the binder weight, of a fatty acid modified glycidyl component comprising the product of polymerization of unsaturated fatty acids, monomers of an ethylenically unsaturated epoxide and monomers selected from the group consisting of C_rC_g alkyl methacrylate, C_rC₈ alkyl acrylate, aromatic vinyl monomers and mixtures thereof, wherein the alkyl groups have 1-8 carbon atoms, wherein the acrylic polymer has a weight average molecular weight of about 2,000 to about 40,000, and wherein the polymer has an epoxide equivalent weight of about 200 to about 1000; and (c) about 20 to about 80 percent by weight, based on the binder weight, of an acrylic polymer having both tertiary amine functionality and hydroxyl functionality comprising the product of polymerization of monomers of hydroxy alkyl acrylate or hydroxy alkyl methacrylate, monomers selected from the group consisting of dialkylamino alkyl acrylate, dialkylamino alkyl methacrylate, alkylamino alkyl methacrylamide, alkyl acrylate, alkyl methacrylate, aromatic vinyl compounds, and mixtures thereof, wherein the alkyl groups have 1-8 carbon atoms, the polymer has a weight average molecular weight of about 2,000 to about 40,000, and wherein the polymer has a tertiary amine equivalent weight of about 200 to about 1000.

In an alternate embodiment of the invention there is provided a coating composition capable of providing a hard, glossy and tack-free finish on cure at ambient temperature. The coating composition comprises about 50 to about 90 percent by weight of reactive binder components and about 10 to about 40 percent by weight of an organic solvent wherein the binder components comprise

(a) about 20 to about 80 percent by weight, based on the binder weight, of a fatty acid modified glycidyl component comprising the product of polymerization of unsaturated fatty acids, monomers of an ethylenically unsaturated epoxide and monomers selected from the group consisting of C_rC₈ alkyl methacrylate, C_rC₈ alkyl acrylate, aromatic vinyl monomers and mixtures thereof, wherein the alkyl groups have 1-8 carbon atoms, wherein the acrylic polymer has a weight average molecular weight of about 2,000 to about 40,000, and wherein the polymer has an epoxide equivalent weight of about 200 to about 1000; and

(b) about 20 to about 80 percent by weight, based on the binder weight, of an acrylic polymer having both tertiary amine functionality and hydroxyl functionality comprising the product of polymerization of monomers of hydroxy alkyl acrylate or hydroxy alkyl methacrylate, monomers selected from the group consisting of dialkylamino alkyl acrylate, dialkylamino alkyl methacrylate, alkylamino alkyl methacrylamide, alkyl acrylate, alkyl methacrylate, aromatic vinyl compounds, and mixtures thereof, wherein the alkyl groups have 1-8 carbon atoms, the polymer has a weight average molecular weight of about 2,000 to about 40,000, and wherein the polymer has a tertiary amine equivalent weight of about 200 to about 1000. The present coating compositions can be applied and cured at ambient or elevated temperate to increase the abrasion resistance and improve the weatherability of a metal, wood or plastic substrate. The composition of the present invention forms an excellent quality clear coating over pigmented finishes or the present composition can itself be pigmented to form a colored finish. The coating exhibits superior adhesion to pigmented finishes; it has excellent humidity resistance, and it is otherwise weatherable and durable. Both pigmented and unpigmented coating compositions of the present invention are useful for finishing and refinishing the exterior of industrial, agricultural, and construction equipment, automobiles, tanks, and trucks, and to provide durable coatings for structures such as bridges, buildings, for example, factories and oil refineries, appliances, metal furniture and the like. The coating composition can also be used for finishing plastic substrates. Preferably, the coating composition is formulated to have a high solids content; it typically contains about 40 to about 80 percent by weight binder and about 20 to about 60 percent by weight of organic solvent. The binder of the composition generally contains about 0 to about 24 percent by weight of anhydride acrylic polymer containing at least two anhydride groups, about 5 to about 50 percent by weight of a fatty acid modified glycidyl-containing component with at least two reactive glycidyl groups and two reactive unsaturation sites, and about 5 to about 60 percent by weight of a polymeric component containing multiple hydroxyl groups. It can be catalyzed by use of an external catalyst, e.g., one co-applied with the coating composition or it can be an internal catalyst, e.g., one incorporated into the polymer chain of the hydroxy functional reactive binder component.

When the present composition contains an anhydride acrylic polymer, the polymer typically has a weight average molecular weight of about 2,000 to about 50,000 determined by gel permeation chromatography using polystyrene as a standard and, preferably, has a weight average molecular weight of about 3,000 to about 25,000. The anliydride acrylic polymer is prepared by conventional techniques in which the monomers, solvent, and conventional catalysts such as dicumyl peroxide are charged into a polymerization vessel and heated to about 75-200°C for about 0.5-6 hours to form the polymer.

The anhydride acrylic polymer is formed by polymerizing monomers of alkyl methacrylates, or alkyl acrylates or mixtures thereof, wherein the alkyl groups have 1-12 carbon atoms and ethylenically unsaturated anhydrides (or ethylenically unsaturated dicarboxylic acids which are converted to the acid anhydride during polymerization). Optionally, the anhydride acrylic polymer can contain other components such as styrene, alpha. -methyl styrene, acrylonitrile, methacrylonitrile in amounts of about 0.1 to about 50 percent by weight.

Typical alkyl acrylates and methacrylates that can be used to form the anhydride acrylic polymer are methyl methacrylate, ethyl methacrylate, ethylhexyl acrylate, propyl methacrylate, butyl methacrylate, pentyl methacrylate, hexyl methacrylate, octyl methacrylate decyl methacrylate, lauryl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, octyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate and the like. Other components that can be used to form the anhydride acrylic polymer are acrylamide, methacrylamide, acrylo alkoxy silanes, such as gamma methacryloyl propyl trimethoxy silane. Also the anhydride acrylic polymer can contain about 0J to about 5 percent by weight of an ethylenically unsaturated acid such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, and the like. Typically, useful ethylenically unsaturated anhydrides include itaconic anhydride, maleic anhydride, isobutenyl succinic anhydride, and the like. It is also possible to impart the anhydride functionality to the anhydride acrylic polymer by using the appropriate ethylenically unsaturated dicarboxylic acid which converts to the corresponding acid anhydride by simple heating. Ethylenically unsaturated dicarboxylic acids that can be used in accordance with the present invention are itaconic acid, maleic acid, isobutenyl succinic acid, and the like.

Preferred anhydride acrylic polymers include styrene/methyl methacrylate/butylacrylate/maleic anhydride, methyl methacrylate/butyl acrylate/itaconic anhydride, butyl acrylate/styrene/maleic anhydride/maleic acid, and methyl methacrylate/butyl acrylate/itaconic anhydride. The anhydride equivalent weight is preferably from about 1000 to about 2000. More preferably, the anhydride equivalent weight is from about 1400 to about 1600.

The glycidyl component contains at least two glycidyl groups and can be an oligomer or a polymer. Exemplary glycidyl components include sorbitol polyglycidyl ether, mannitol polyglycidyl ether, pentaerythritol polyglycidol ether, glycerol polyglycidyl ether, low molecular weight epoxy resins such as epoxy resins of epichlorohydrin and bisphenol A, di- and polyglycidyl esters of acids, polyglycidyl ethers of isocyanurates, (e.g., Denecol EX301 from Nagase). Sorbitol polyglycidyl ether (e.g., Araldite XUGY-358.RTM. from Ciba-Geigy), and di- and polyglycidyl esters of acids (e.g., Araldite CY-184.RTM. from Ciba-Geigy), are preferred since they form high quality finishes. Glycidyl methacrylate or acrylate-containing acrylic polymers can also be used such as random and block polymers of glycidyl methacrylate/ethylhexyl acrylate/styrene. The block polymers can be prepared by free radical polymerization, anionic polymerization or by group transfer polymerization. The fatty acid used to modify the glycidyl component can be fatty acids such as a dehydrated caster oil fatty acid, a tall oil fatty acid, a soya oil fatty acid, a linseed oil fatty acid, a coconut fatty acid, and the like. The composition of common vegetable oils that may be used as a source of the fatty acids for use in accordance with the invention is shown in Tables I and II along with the fatty acid content of each.

π. Fatty Acid Compositions of Some of the More Common Negetable Oils (Approximate % Composition)

ypica ta oi atty aci s resin an ey rate castor oi s own or competeness

The residual epoxide equivalent weight for the glycidyl component is preferably from about 200 to about 1000. More preferably, the residual epoxide equivalent weight for the glycidyl component is from about 600 to about 800. The fatty acid equivalent weight is preferably from about 1000 to about 2000. More preferably, the fatty acid equivalent weight is from about 1400 to about 1600. The hydroxy functional polymeric material has a weight average molecular weight of about 3,000 to about 20,000 and has multiple hydroxyl groups. The hydroxyl group containing materials can have a hydroxy value of about 50 to about 300. Typical, but non-limiting, examples thereof are polymeric polyols such as acrylic polyols, polyester polyols, polyesterurethane polyols, polyether polyols, acrylourethane polyols and mixtures thereof.

The acrylic polyols can be formed by polymerizing monomers of alkyl methacrylates or alkyl acrylates or mixtures thereof (where the alkyl groups have 1-12 carbon atoms) and hydroxy-functional alkyl (meth)acrylate (where (meth)acrylate means either acrylate or methacrylate). Optionally, the acrylic polyols contain other components such as styrene, .alpha.-methyl styrene, acrylonitrile, and methacrylonitrile, and the like, in amounts of about 0J to about 50 percent by weight. Typical alkyl acrylates and methacrylates are described above.

Polyesterurethane polyol is the reaction product of a hydroxyl- terminated polyester and a polyisocyanate, preferably, an aliphatic dusocyanate. The urethane has a hydroxyl number of about 75 to about 200 and has a weight average molecular weight of about 3,000 to about 25,000 and a number average molecular weight of about 2,000 to about 6,000 measured using gel permeation chromatography using polystyrene as a standard. The polyester used to form the polyester urethane, for example, is the esterification product of an alkylene glycol, a polyhydric alcohol having at least three hydroxy groups, and an aromatic dicarboxylic acid or its anhydride. Preferably, the polyester has a hydroxyl number of about 100 to about 200. Typical alkylene glycols, polyhydric alcohols and aromatic dicarboxylic acids or its anhydride are described in U.S. Pat. No. 4,614,683. The '683 patent also describes typical polyisocyantes. The amine equivalent weight for the hydroxy functional polymer is from about 200 to about 1000. More preferably, the amine equivalent weight is from about 600 to about 800. The hydroxy equivalent weight is from about 400 to about 1200. More preferably, the hydroxy equivalent weight is from about 800 to about 1000.

About 0 to about 5 percent by weight, based on the weight of the binder of the coating composition, of an external catalyst can be added to enhance curing rate of the composition. Exemplary of catalysts for use in accordance with the present invention are triethylene diamine, quinuclidine, dialkyl alkanol amines such as dimethyl ethanolamine, diethyl ethanol amine, dibutyl ethanol amine, diethyl hexanol amine and the like, lithium tertiary butoxide, tri(dimethylaminomethyl)phenol, bis(dimethylamino)propan-2-ol, N.N.N^N'-tetramethylethylenediamine, N,methyldiethanolamine, N,N-dimethyl-l,3-propanediamine and 1-dimenthylamino- 2-propanol or quaternary ammonium salts such as tert-butyl ammonium bromide, benzyl trimethyl ammonium formate and the like. Preferably, the catalyst can be incorporated in the polymeric chain of the hydroxy functional reactive binder component by using amino-functional alkyl acrylates such as 2-dimethyl amino ethyl methacrylate, 2-diethyl amino ethyl methacrylate, vinyl pyridine, and tert-butyl amino ethyl methacrylate. Alternatively, the catalyst need not be added to the coating composition, but instead, after an article is coated, the article can be passed into a chamber containing catalyst vapors. Dimethylethanol amine is a catalyst that can be vaporized and used to cure the coating composition. In still another embodiment of the invention, to achieve curing, the catalyst may be sprayed with the coating composition using a dual spray gun.

Solvents for use in preparing the anliydride acrylic polymer and for use as a diluent for the coating composition include toluene, xylene, butyl acetate, methyl amyl ketone, ethyl benzene, higher boiling point aromatic hydrocarbons, amyl acetate, ethyl acetate, propyl acetate, and ethylene or propylene glycol mono alkyl ether acetates.

In addition, certain alcoholic solvents are also useful in accordance with the present invention. The alcoholic solvents under certain use conditions convert portions of the anhydride to half-esters also useful as reactants in the system of the present invention. Examples of such alcohols are propanol, isobutanol, methanol, isopropanol, tertiary butanol, n-butanol, propylene glycol monomethyl ether, ethylene glycol monobutyl ether, and other alcoholic solvents. The coating composition comprises about 20 to about 80 percent by weight of solvent. To improve weatherability of the clear finish of the coating composition, about 0J to about 5 percent, by weight, based on the weight of the binder, of an ultraviolet light stabilizer or mixtures thereof can be added. These stabilizers include ultraviolet light absorbers, screeners, quenchers and specific hindered amine light stabilizers. Also, about 0J to about 5 percent by weight, based on the weight of the binder, of an antioxidant can be added.

Typical ultraviolet light stabilizers useful in accordance with the present invention include benzophenones such as hydroxydodecyclobenzophenone, 2,4-dihydroxybenzophenone, hydroxy-benzophenones containing sulfonic acid groups, 2,4-dihydroxy-3',5'-di-t-butylbenzophenone, 2,2',4'-trihydroxybenzophenone esters of dicarboxylic acids, 2-hydroxy-4-acryloxyethoxybenzophenone, aliphatic mono-esters of 2,2',4-trihydroxy-4'-alkoxybenzophenone, 2-hydroxy-4-methoxy-2,- carboxybenzophenone; triazoles such as 2-phenyl-4-(2,-4,- dihydroxybenzoyl)triazoles, substituted benzotriazoles such as hydroxyphenyltriazoles such as 2-(2'hydroxy-5'-methylphenyl) benzotriazole, 2- (2'hydroxyphenyl)benzo-triazole, 2-(2'-hydroxy-5^,-octylphenyl)naphthotriazole; triazines such as 3,5-dialkyl-4-hydroxyphenyl derivatives of triazine, sulfur- containing derivatives of dialkyl-4-hydroxyphenyltriazines, hydroxyphenyl-1,3,5- triazines and such triazines containing sulfonic acid groups, aryl-l,3,5-triazines, orthohydroxyaryl-s-triazine; benzoates such as dibenzoate of diphenylolpropane, t- butyl benzoate of diphenylolpropane, nonyl phenyl benzoate, octyl phenyl benzoate, and resorcinol dibenzoate.

Other ultraviolet light stabilizers that are useful in the invention include lower alkyl thiomethylene-containing phenols, substituted benzenes such as l,3-bis(2'-hydroxybenzoyl)benzene, metal derivatives of 3,5,-di-t-butyl-4- hydroxyphenylpropionic acid, asymmetrical oxalic acid diarylamides, alkylhydroxyphenylthioalkanoic acid esters, dialkylhydroxyphenylalkanoic acid esters of di- and tri-pentaerythritol, phenyl- and naphthlenesubstituted oxalic acid diamides, methyl- .beta. -(3 , 5-di-t-butyl-4-hydroxyphenyl)propionate, . alpha. , . alpha. '-bis(2- hydroxy-phenyl)diisopropylbenzene, 3,5'-dibromo-2'-hydroxy-acetophenone, ester derivatives of 4,4-bis(4'-hydroxy-phenyl)pentaonic acid wherein there is at least one unsubstituted position ortho to the aromatic hydroxyl groups, organophosphorus sulfides such as bis(diphenyl-phosphinothioyl)monosulfide and bis(diphenyl- phosphinothioyl)disulfide, 4-benzoyl-6-(dialkylhydroxybenzyl)resorcinol, bis(3- hydroxy-4-benzoylphenoxy)diphenylsilane, bis(3-hydroxy-4-benzoylphenoxy) dialkylsilane, l,8-naphthalimides,.alpha.-cyano- .beta.,.beta.-diphenylacrylic acid derivatives, bis(2-benzoxazolyl)alkanes, bis(2-naphthoxazolyl)alkanes, methylene malonitriles containing aryl and heteroacyclic substitutes, alkylenebis(dithio)carbamate, 4-benzoyl-3-hydroxyphenoxyethyl acrylate, 4-benzoyl- 3- hydroxyphenoxyethyl-methacrylate, aryl or alkyl-substituted acrylonitriles, 3- methyl-5-isopropylphenyl-6-hydroxycourmarone, and 8-acetyl-3-dodecyl-7,7,9,9- tetramethyl-l,3,8-triazasprio(4,5)decanol-2,4-d ione.

Particularly useful ultraviolet light stabilizers are hindered amines of piperidyl derivatives such as those disclosed in U.S. Pat. No. 4,061,616 incorporated herein by reference, and nickel compounds such as [l-phenyl-3-methyl-4- decanoylpyrazolate(5)]-Ni, bis[phenyldithiocarbamato]-Ni(II), and others listed in the '616 patent.

The following blend of ultraviolet light stabilizers is exemplary of a light stabilizer composition that can be used in the invention. Such a composition includes 2-[2'-hydroxy-3',5'-l(l-l-dimethyl-propyl)phenyl]benzotrizole and bis-[4- (1,2,2,6,6-pentamethylpiperidyl)] 2-butyl-2-[(3,5-t-butyl-4-hydroxyphenyl)methyl] propanedioate. The stabilizers can be used in any ratio, however, a 1:1 ratio of benzotriazole to propanedioate is preferred. Another useful blend of ultraviolet light stabilizers is 2-(benzotriazole-2-NL)-4,6-bis(methyl-ethyl-l -phenyl ethyl)phenol, and 2(3 hydroxy-3,5'-ditert amyl phenyl) benzotriazole.

The composition can be pigmented to form a colored finish or a primer. About 0J to about 200 percent by weight, based on the weight of the binder, of pigment can be added. Pigments may be of any conventional type, such as, for example, iron oxides, lead oxides, strontium chromate, carbon black, coal dust, titanium dioxide, talc, barium sulfate, as well as color pigments such as cadmium yellow, cadmium red, chromium yellow and metallic pigments such as aluminum flake. The pigment can be added using conventional techniques in which a mill base- containing pigment, dispersant, and solvent is first mixed. The mill base is then mixed with the coating composition to form a colored composition. This composition can be applied and cured as described below. In addition, various fillers, plasticizers, anti-oxidants, ultraviolet light absorbers, flow control agents, surfactants and other formulating additives can be employed if desired.

In one embodiment of the invention a method for increasing the abrasion resistance and improving the weatherability of a metal or plastic substrate is provided. The method comprises the steps of mixing the components of any of the coating compositions described above, applying the mixture to a metal or plastic substrate, and curing the coating composition at ambient temperature or by heating. The components of the coating composition of the present invention can be mixed and applied to the substrate immediately thereafter. Alternatively, the components can be mixed, and the coating composition applied to the substrate after waiting for any period of time. For example, the coating composition can be applied to the substrate after waiting for a period of time during which the substrate is prepared for application of the coating composition. Generally, when used as a clear or pigmented coating, the composition is applied by conventional techniques such as air atomized spray, high volume low pressure spray, airless spray, air assisted airless spray, electrostatic air atomized spray, electrostatic bell, electrostatic disk, roll coating, reverse roll coating, curtain coating, dipping, or flow coating. For the application to plastic sheets, spray application, rollcoating, or curtain coating are preferred. The viscosity of the coating may be adjusted by the selection and addition of suitable solvents as is well known to those skilled in the art of coating formulations and their application. Further the coating composition of the present invention may be used as the sole film-forming composition on the substrate, or may be utilized as a primer or adhesion promoting layer for subsequent applications.

The resulting coating can be dried and cured at ambient temperatures, or it can be cured at elevated temperatures of about 60 to about 200°C. Generally, the coatings are baked at about 60 to about 140°C for about 10 to about 40 minutes or are dried at ambient temperatures. At ambient temperatures, the coating dries to a tack- free condition in about 180 minutes and in about 24 hours the coating is substantially cured. In about 5-7 days, the coating is completely cured. Coatings are applied to form a finish about 0.5 to about 5 mils thick, and, preferably, about 1 to about 2 mils thick. The finish has excellent gloss, superior adhesion to substrate, excellent weatherability, and high solids.

The invention is further described by reference to the following examples. These examples are illustrative of the present invention and are not intended to limit the scope of the invention in any manner. All parts and percentages are on a weight basis unless indicated otherwise. Molecular weights are determined by gel permeation chromatography using polystyrene as the standard.

EXAMPLE 1

Anhydride Acrylic Polymer-

The following constituents were charged into a reactor with a thermocouple, stirrer, addition funnel, nitrogen induction tube, and condenser:

Parts by Weight

Portion 1

Methyl Amyl Ketone 23.4

Portion 2

Maleic Anhydride 4.6

Styrene 19.5

Methyl Methacrylate 11.5

Butyl Methacrylate 34.9

Portion 3

Methyl Amyl Ketone 2.6

Dicumyl Peroxide 3.3

Portion 4

Methyl Amyl Ketone 0J8

Dicumyl Peroxide 0.02 Portion 1 was charged to the reactor, covered with a nitrogen blanket and heated to 145°C. Portion 2 was added dropwise over a 360 minute period. Portion 3 was added simultaneously with portion 2. After completion of the addition, the resulting composition was held at 145°C for 1 hour. Portion 4 was then added over a 5 minute period after completion of the 1 hour hold.

The resulting polymer composition was reduced to 60-62 percent weight solids with Methyl Amyl Ketone. The resulting polymer composition had a Gardner-Holdt viscosity of I-L. The polymer composition had a weight average molecular weight of 5900. The theoretical anhydride equivalent weight is 1502.

Gylcidyl Component Polymer-

The following were charged into a reactor equipped with a thermocouple, stirrer, addition funnel, nitrogen induction tube and condenser:

Parts by Weight

Portion 1

Methyl Amyl Ketone 25.7

Portion 2 Styrene 15.6

2-Ethylhexyl Acrylate 18.2 Glycidyl Methacrylate 23.4

Portion 3

Methyl Amyl Ketone 1.8

Dicumyl Peroxide 2.0

Portion 4

Methyl Amyl Ketone 0.1 Dicumyl Peroxide 0.1

Portion 5 Dehydrated Castor Oil Fatty Acid 13.1 Triphenyl Phosphine 0.0004 Portion 1 was charged into the reactor, covered with a nitrogen blanket and heated to 145°C. Portion 2 was added dropwise over a 240 minute period. Portion 3 was added simultaneously with portion 2. After completion of the addition, the resulting composition was held at 145°C for 1 hour. Portion 4 was then added over a 5 minute period after completion of the 1 hour hold. The resulting composition was then cooled to less then 100°C. Portion 5 was then added over a 5 minute period and the temperature was raised to 145°C. The resulting composition was held at 145°C until an acid value less than 1 was obtained.

The resulting polymer composition was reduced to 65-68 percent weight solids with Methyl Amyl Ketone. The resulting polymer composition had a Gardener-Holdt viscosity of T-X. The resulting polymer composition had a weight average molecular weight of 24000. The theoretical residual epoxide equivalent weight and the theoretical fatty acid equivalent weight are 1508 and 595, respectively.

Hydroxy Functional Polymer-

The following constituents were charged into a reactor equipped with a thermocouple, stirrer, addition funnel, nitrogen induction tube, and condenser:

Parts by Weight

Portion 1

Methyl Amyl Ketone 23.3

Portion 2

Styrene 21.3

Hydroxyethyl Methacrylate 9.9

Dimethyl-

Aminoethyl Methacrylate 15

Butyl Acrylate 17.7

Methyl Methacrylate 3.6

Portion 3

Methyl Amyl Ketone 5.6

2,2 ' -azobis(methylbutyronitrile) 3.6

Portion 4

Methyl Amyl Ketone 0.004

2,2'-azobis(methylbutyronitrile) 0.002 Portion 1 was charged into the reactor, covered with a nitrogen blanket and heated to 110°C. Portion 2 was added dropwise over a 360 minute period. Portion 3 was added simultaneously with portion 2. After completion of the addition, the resulting composition was held at 110°C for 1 hour. Portion 4 was then added over a 5 minute period after completion of the 1 hour hold.

The resulting polymer composition was reduced to 60-62 percent weight solids with Methyl Amyl Ketone. The resulting polymer composition had a Gardener-Holdt viscosity of O-R. The resulting polymer composition had a weight average molecular weight of 8100. The theoretical hydroxy equivalent weight and the theoretical amine equivalent weight are 886 and 706, respectively. The experimental amine equivalent weight is 715.

EXAMPLE 2

A clear coating composition was prepared by thoroughly blending together the following constituents:

Portion 1 Parts by Weight

Hydroxy Containing 40

Polymer Composition

(prepared above)

Methyl Amyl Ketone 59

Flow Additive 1

Portion 2

Glycidyl Component Polymer 40

(prepared above)

Methyl Amyl Ketone 60

The resulting coating composition had a solids content of 40% to 50% and a viscosity of 15-30 seconds measured with a No. 3 EZ cup. Portion 1 and Portion 2 were mixed at an epoxy equivalent weight to amine equivalent weight of 0.5 to 20.0, preferably 1.0 to 1.5 and the coating composition was applied onto a metal panel and cured for 20 minutes at 180°C. The resulting film was hard and glossy and withstood greater than 100 double rubs with methyl ethyl ketone.

EXAMPLE 3 A pigmented coating composition was prepared by thoroughly blending together the following constituents:

Portion 1 Parts by Weight

Hydroxy Containing 40

Polymer Composition

(prepared above)

Methyl Amyl Ketone 47.7

Dispersant 1.5

UN stabilizer 0.4

Flow additive 1.0

Titanium Dioxide 9.4

Portion 2

Glycidyl Component Polymer 40

(prepared above)

Methyl Amyl Ketone 60

The resulting coating composition had a solids content of 40% to 60%, and a viscosity of 15-30 seconds measured with a No. 3 EZ cup. Portion 1 and Portion 2 were mixed at an epoxy equivalent weight to amine equivalent weight of 0.5 to 20.0, preferably 1.0 to 1.5 and the coating composition was applied onto a metal panel and cured for 20 minutes at 180°C. The resulting film was hard and glossy and withstood greater than 100 double rubs with methyl ethyl ketone.

Claims

CLAIMS:

1. A coating composition having a hard, glossy and tack-free finish comprising about 20 to about 80 percent by weight of a solvent and about 20 to about 80 percent by weight of reactive binder components wherein the binder components comprise

(a) 0 to about 24 percent based on the binder weight of an anhydride acrylic polymer having at least two reactive anhydride groups and comprising the product of polymerization of monomers of an ethylenically unsaturated anhydride or an ethylenically unsaturated dicarboxylic acid and monomers selected from the group consisting of C_rC₈ alkyl methacrylate, C_rC₈ alkyl acrylate, vinyl monomers and mixtures thereof, said acrylic polymer having a weight average molecular weight of about 2,000 to about 50,000;

(b) about 5 to about 50 percent based on the binder weight of a fatty acid modified glycidyl polymer component having hydroxy functionality and at least two reactive glycidyl groups and at least two reactive unsaturation groups; and

(c) about 5 to about 60 percent based on the binder weight of a polymeric component containing multiple hydroxy groups, said polymer component selected from the group consisting of acrylic polyols, polyester polyols, polyesterurethane polyols, polyether polyols, acrylourethane polyols and mixtures thereof, having a weight average molecular weight of about 3,000 to about 20,000, and about 0J to about 15 percent based on the binder weight of a tertiary amine catalyst incorporated into the polymer component.

2. The coating composition of claim 1 in which the glycidyl component is selected from the group consisting of a polyglycidyl ether of a low molecular weight polyol, an epoxy resin of epichlorohydrin and bisphenol A, a polyglycidyl ester of polyacids, polyglycidyl ethers of isocyanurates, a glycidyl methacrylate or a glycidyl acrylate containing acrylic polymer, and mixtures thereof.

3. The coating composition of claim 1 wherein the glycidyl polymeric component is modified with a fatty acid selected from the group consisting of a dehydrated caster oil fatty acid, a tall oil fatty acid, a soya oil fatty acid, a linseed oil fatty acid, and a coconut fatty acid.

4. The coating composition of claim 1 wherein the anhydride acrylic polymer contains about 0J to about 50 percent by weight of monomers selected from the group consisting of styrene, acrylonitrile, methacrylonitrile and mixtures thereof.

5. The coating composition of claim 1 in which the anhydride acrylic polymer has a glass transition temperature of 0 to 75° C and a weight average molecular weight of about 3,000 to about 25,000.

6. The coating composition of claim 1 wherein the anhydride acrylic polymer consists essentially of about 20 to about 40 percent by weight, based on the weight of the acrylic polymer, of methyl methacrylate, styrene,. or mixtures thereof, about 35 to about 55 percent by weight of an alkyl methacrylate or an alkyl acrylate having 2-4 carbon atoms in the alkyl group and about 5 to about 55 percent by weight of polymerizable ethylenically unsaturated anhydride or ethylenically unsaturated dicarboxylic acid.

7. The coating composition of claim 1 wherein the polymeric component containing multiple hydroxy groups is a polymer comprising polymerized monomers of a hydroxy alkyl methacrylate or an hydroxy alkyl acrylate and polymerized monomers selected from the group consisting of alkyl methacrylate, alkyl acrylate and mixtures thereof, wherein the alkyl groups have 1-12 carbon atoms and the polymer has a weight average molecular weight of about 3,000 to about 20,000.

8. The coating composition of claim 6 wherein the polymeric component containing multiple hydroxy groups contains about 0J to about 50 percent by weight of monomers selected from the group consisting of styrene, acrylonitrile, methacrylonitrile, and mixtures thereof.

9. The coating composition of claim 6 wherein the catalyst is incorporated into the polymeric component containing multiple hydroxyl groups by using tertiary amino functional alkyl acrylates or methacrylates.

10. The coating composition of claim 1 wherein the polyesterurethane polyol is the reaction product of a polyisocyanate and a polyester which is the esterification product of an alkylene glycol, a polyhydric alcohol having at least three hydroxyl groups and an aromatic dicarboxylic acid or its anhydride.

11. The coating composition of claim 9 wherein the polyesterurethane polyol has a hydroxyl number of about 75 to about 200 and a weight average molecular weight of about 3,000 to about 20,000.

12. The coating composition of claim 6 wherein the glycidyl component is a polymer component comprising polymerized monomers of a glycidyl acrylate or glycidyl methacrylate and polymerized monomers selected from the group consisting of alkyl acrylates, alkyl methacrylates, and mixtures thereof.

13. The coating composition of claim 11 wherein the glycidyl polymeric component contains about 0J to about 50 percent by weight of monomers selected from the group consisting of styrene, acrylonitrile, methacrylonitrile, and mixtures thereof.

14. The coating composition of claim 11 wherein the glycidyl polymeric component is modified with a fatty acid selected from the group consisting of a dehydrated caster oil fatty acid, a tall oil fatty acid, a soya oil fatty acid, a linseed oil fatty acid, and a coconut fatty acid.

15. The coating composition of claim 11 wherein the anliydride acrylic polymer consists of polymerized monomers of methyl methacrylate and butyl acrylate.

16. The coating composition of claim 11 wherein the anhydride acrylic polymer consists of polymerized monomers of butyl acrylate, styrene, maleic anliydride and maleic acid.

17. The coating composition of claim 5 wherein the anhydride acrylic polymer consists essentially of polymerized monomers of methyl methacrylate, styrene, maleic anhydride, maleic acid and butyl acrylate and the glycidyl component consists essentially of polymerized monomers of glycidyl methacrylate, styrene, 2-ethylhexyl acrylate, and is modified with a dehydrated castor oil fatty acid.

18. The coating composition of claim 1 containing about 0J1 to about 200 percent by weight, based on the weight of the binder, of pigment.

19. A coating composition having a hard, glossy and tack-free finish comprising about 50 to about 90 percent by weight of reactive binder components and about 10 to about 40 percent by weight of an organic solvent wherein the binder comprises

(a) about 1 to about 20 percent by weight, based on the binder weight, of an anhydride acrylic polymer having at least two reactive anhydride groups and comprising the product of polymerization of monomers of an ethylenically unsaturated anhydride and monomers selected from the group consisting of C_rC₈ alkyl methacrylate, C_rC_g alkyl acrylate, aromatic vinyl monomers and mixtures thereof, wherein the alkyl groups have 1-8 carbon atoms and wherein said acrylic polymer has a weight average molecular weight of about 2,000 to about 40,000; (b) about 20 to about 80 percent by weight, based on the binder weight, of a fatty acid modified glycidyl component comprising the product of polymerization of unsaturated fatty acids, monomers of an ethylenically unsaturated epoxide and monomers selected from the group consisting of C_rC₈ alkyl methacrylate, C_rC₈ alkyl acrylate, aromatic vinyl monomers and mixtures thereof, wherein the alkyl groups have 1-8 carbon atoms, wherein said acrylic polymer has a weight average molecular weight of about 2,000 to about 40,000, and wherein the polymer has an epoxide equivalent weight of about 200 to about 1000; and

(c) about 20 to about 80 percent by weight, based on the binder weight, of an acrylic polymer having both tertiary amine functionality and hydroxyl functionality comprising the product of polymerization of monomers of hydroxy alkyl acrylate or hydroxy alkyl methacrylate, monomers selected from the group consisting of alkylamino alkyl acrylate, alkylamino alkyl methacrylate, alkylamino alkyl methacrylamide, alkyl acrylate, alkyl methacrylate, aromatic vinyl compounds, and mixtures thereof, wherein the alkyl groups have 1-8 carbon atoms, the polymer has a weight average molecular weight of about 2,000 to about 40,000, and wherein the polymer has a tertiary amine equivalent weight of about 200 to about 1000.

20. A coating composition having a hard, glossy and tack-free finish comprising about 50 to about 90 percent by weight of reactive binder and about 10 to about 40 percent by weight of an organic solvent wherein the reactive binder comprises

(a) about 20 to about 80 percent by weight, based on the binder weight, of a fatty acid modified glycidyl component comprising the product of polymerization of unsaturated fatty acids, monomers of an ethylenically unsaturated epoxide and monomers selected from the group consisting of C_rC₈ alkyl methacrylate, C_rC₈ alkyl acrylate, aromatic vinyl monomers and mixtures thereof, wherein the alkyl groups have 1-8 carbon atoms, wherein said acrylic polymer has a weight average molecular weight of about 2,000 to about 40,000, and wherein the polymer has an epoxide equivalent weight of about 200 to about 1000; and

(b) about 20 to about 80 percent by weight, based on the binder weight, of an acrylic polymer having both tertiary amine functionality and hydroxyl functionality comprising the product of polymerization of monomers of hydroxy alkyl acrylate or hydroxy alkyl methacrylate, monomers selected from the group consisting of alkylamino alkyl acrylate, alkylamino alkyl methacrylate, alkylamino alkyl methacrylamide, alkyl acrylate, alkyl methacrylate, aromatic vinyl compounds, and mixtures thereof, wherein the alkyl groups have 1-8 carbon atoms, the polymer has a weight average molecular weight of about 2,000 to about 40,000, and wherein the polymer has a tertiary amine equivalent weight of about 200 to about 1000.